Windows Installer keeps popping up

I recently installed a shareware program on my Windows 2000 machine that used Windows Installer to install
it.  After it got done, a window kept popping up whenever I tried to click on My Computer, IE 6.0, and
many other programs.  Also, when I try to open any Office 2000 program, after I get the 'preparing to
install' window I receive a Problem wiht Shortcut box saying "The Windows Installer service could not
be accessed.  Contact your support personnel to verify that the Windows Installer service is properly
registered."
  I have checked under service and the Windows Installer service is not running.  It will not start.
When I try to start it, it says "Could not start the Windows Installer service on Local Computer. Error
5: Access is denied."  
  When I try to double click the file that is listed in the properties of the services window (msiexec.exe),
I get an error saying 'incorrect command line parameters'.  The only parameters that I can find is in
the properties of the Services window - it has the file name with a /V which is verified on the Microsoft
website.
  I have followed both Q315353 and Q315346 from the Microsoft Support site.  They are for XP, but I
hoped they would work for me since I could not find anything for 2000.  
  I know this is a lot of info, but I tried to be as thorough as I could.  I really don't want to reformat
my computer and any help would be greatly appreciated!
  Thanks!  - Jon